Enameled sheet metal and method of making said sheet metal



Patented Dec. 22, 1936 PATENT OFFICE v ENALIELED SHEET METAL AND. DIETHOD OF MAKING SAID SHEET METAL Rudyard Porter, Minneapolis, Minn, and Raymond B. Saylor, Oakmont, P

a., assignora to American Sheet and Tin Plate Company, a corporation of New Jersey No Drawing.

Application'November 27, 1935. Serial No. 51,971

5 Claims. (01- 29-18) This invention relates to sheet metal and more particularly to the manufacture of low-metalloid metals which are adapted to be subsequently coated with vitreous enamel. Such metals are 5 composed of iron containing low percentages of impurities such as carbon, manganese phosphorus,'sulphur and silicon. This is especially true of carbon and manganese.

. In the manufacture of vitreous enameled ar- 10 ticles, it is the general practice to form the metal into sheets, or articles, and thereafter apply the enamel coating by sintering or fusing. 'As' a rule, sheets or articles which are coated with vitreous enamel must have a final smooth and 15 unbroken surface if they are to be acceptable.

According to the conventional methods of making the sheets or articles which are to be subsequently coated with vitreous enamel, numerous defects appear at certain stages in the 2 enameling operations. These defects are generally known as "rebelling" characteristics in the form of black spots", "fish scales", copper heads, etc., and are traceable to the base metal wherein gases are generated and released during 25 the sintering or fusing of the enamel coating.

Certain developments have tended toward the production of sheet metal devoid of these "reboiling characteristics, but their results are inconsistent.

30 .It is one of the objects of the present invention to provide a novel method of producing sheet metal of the low-metalloid variety which is consistently free of "reboiling characteristics when subsequently coated with vitreous enamel.

35 Another object is to provide a'novel method oi. obtaining "killed sheet metal of the lowmetalloid variety, which may be severely coldreduced according to modern methods and at the same time be free from reboiling" char- 40 acteristics and retain its shape when subsequently enameled.

According to the method of the invention,

.metal-having the following approximate analysis is produced:

' 45 Per cent Car n .03 Manganese I .12 Phosphorus .01 Sulphur .02

Silicon .015

Remainder-Iron The carbon and manganese content should be as low. as possible, averaging around .02% and .06%, respectively. In no instance should the carbon bein excess of .08% and the manganese above 25%. a

The metal may be produced, by way of ex-. ample, in a basic open-hearth furnace, tapped into a ladle, and thenceteemed into molds. 5 During either the tapping or teeming (and preferably the former) the molten metal is deoxidlzed by additions of deoxidizing agent such as aluminum or ferro-sillcon (preferably the latter) to produce what is commonly known as killed steel. After the metal has been solidified in the. molds, the killedingots are reheated and rolled into slabs or sheet-bar. In the event the ingots are rolled into slabs they are reheated and then continuously rolled in a series of hot-reducing mills into strip form, after which it is coiled.

The coiled strip is then pickled and subjected to'conventional cold-rolling operations wherein severe reductions are efl'ected.

This cold reduction must be of a'high percentage (such as, for example, not less than approximately and preferably around 85%) in order to impart to the metal the desired no-n boiling characteristics hereinbefore discussed. 2

If the cold reduction of this low-'metalloid and killed metal is not severe, boiling tendencies will be present and take form at the time of firing the enamel coating.

After the sheet metal has been reduced to the so desired thickness it may be heat-treated in order to impart drawing or forming characteristics. The metal sheets, or formed articles, are then provided with one or more coatings of enamel which is fused or sintered into their surfaces by firing at elevated temperatures. The sheet metal of the invention is consistently free from reboiling characteristics, as the base metal does not evolve troublesome gases during the enameling operations. In addition, sheet so produced will remain exceptionally flat, which is a highly desirable characteristic for many enameled products.

While we have shown and described certain specificembodiments of our invention, it is to be understood that we do not wish to be limited exactly thereto, since various modifications may be made without departing from the scope of our invention, as defined by the following claims. We claim: g '1. The method of producing sheet metal for subsequent enameling which includes obtaining a'low-metalloidmolten metal having not over .08% carbon and 35% manganese, deoxidizing said molten metal, and cold-reducing said metal not less than 30% in thickness.

2. The method ofproducin'g sheet metal for subsequent enameling which includes obtaining a low-metalloid molten metal having approximately .0292; carbon and approximately .06% manganese. deoxidizing said molten metal, and cold-reducing said metal not less than 30% in thickness.

3. The method of producing sheet metal for subsequent enameling which includes obtaining a low-metalloid molten metal having approximately .02% carbon and'approximately .06% manganese, deoxidizing said molten metal with ierro silicon and cold-reducing said metal not less than 30% in thickness.

4. A severely cold reduced article of killed steel having a surface free from boiling characteristics and an enameled coating on said surface.

5. An article of manufacture comprising a base metal and a coating for said base metal, said base metal comprising a severely" cold reduced killed steel having a surface free from boiling characteristics.

RUDYARD PORTER. RAYMOND B. SAYLOR. 

